I need to do file uploading from surgeons. How large of a file can I securely upload with a paid account?

You can use the File upload field on the form to upload files. Please note that if you want a single file to be uploaded, the max file size is 1 GB. Else, if you want to allow multiple files to be uploaded via the form, then you can allow up to 25 files with the individual max file size of 100 MB.

Here is a useful guide: https://www.jotform.com/help/33-changing-the-file-upload-size-limit

Now based on this you will need a paid account as on Free accounts, the max upload space limit provided is 100 MB.

For Bronze plan, the space limit is 10 GB.

For Silver plan, the space limit is 100 GB.

For Gold plan, the space limit is 1 TB.

Here are the other features per plan: https://www.jotform.com/pricing/

Based on this you can decide which plan you want to upgrade to: https://www.jotform.com/help/331-how-to-upgrade-my-account

Do review and let us know if you have any further questions/concerns.